Research on the Factors Affecting Nitrification Inhibition of Dicyandiamide(DCD) in Latosol

[Objective] This research aimed at studying the effects of application amount of DCD and physics and chemistry characteristics of soil such as temperature,moisture content,organic matter content and pH on the inhibition of nitrification when applying nitrification inhibitor DCD in latosol.[Method] The experiment was carried out under aerobic incubated conditions.[Result] A significant delay period of nitrification was observed when the application amount of DCD was 10 mg/kg soil,and the inhibition can at least last for 56 d.When the cultural temperature had increased from 10 to 30 ℃,the duration of nitrification inhibition was shortened from 90 to 30 d.The nitrification inhibition of DCD was reduced with the increasing soil moisture content,organic matter content and soil pH,while the duration of nitrification inhibition was prolonged with the decreasing soil moisture content,organic matter content and soil pH.[Conclusion] Nitrification inhibition of DCD can be improved by increasing the application amount or reducing soil temperature,moisture content,organic matter content and pH.

Curing Reaction Kinetics of Epoxy Resin Using Dicyandiamide Modified by Aromatic Amines

The curing reaction and reaction mechanism of epoxy resin E-44, for which aromatic amine modified dicyandiamide was used as a curing reagent, were investigated by means of differential scanning calorimetry （DSC）. The results showed that the modified dicyandiamide had better curing characteristic than unmodified dicyandiamide for epoxy resin E-44, and the curing reaction could be carried out at moderate temperature. Apparent activation energy of the curing reaction was decreased appreciably from 123.829 kJ/mol to 61.550-64.405 kJ/mol, and reaction order was decreased from 0.941 to 0.896-0.900. Curing reaction mechanism also was discussed.

Dicyandiamide Sorption-Desorption Behavior on Soils and Peat Humus

The sorption-desorption behavior of dicyandiamide (DCD) is an importantchemical process that affects DCD fate and mobility in soils. Therefore, this study quantified DCDsorption-desorption on a phaeozem (Mollisol), a burozem (Alfisol), a soil with organicmatter-removed and peat humus using the batch-equilibration procedure, and identified soilproperties that influenced DCD sorption. The sorption on peat humus was higher than that on thephaeozem and the burozem, with much lower sorption observed on the soil with organic matter-removed,indicating that soil organic matter was the main carrier of DCD sorption. Due to its amphipathicproperty the DCD molecule sorption on the phaeozem and the burozem decreased as pH increased fromabout 2 to 5, but a further increase in pH led to a rise in DCD sorption. The DCD desorptionhysteretic effect for peat humus was greater than that for the phaeozem and the burozem using 0.01mol L^(-1) CaCl_2 as the background electrolyte, suggesting that the hydrophobic domains of organicmatter may play an important role in DCD sorption.

Synthesis and Efficiency of a SphericalMacroporous Epoxy-dicyandiamide ChelateResin for Preconcentrating and SeparatingTrace Au, Hg, Pd and Ru from Samples

A novel spherical macroporous epoxy-dicyandiamide chelate resin was synthesized simply and rapidly from epoxy resin and used for the preconcentration and separation of trace amounts of Au (Ⅲ ), Hg (Ⅱ ), Pd (Ⅳ) and Ru (Ⅲ) ions from solution samples. The analyzed ions can be quantitatively concentrated by the resin at a flow rate of 2. 0 mL/min at pH 4, and can also be desorbed with 15 mL of 4 mol/L HCl + 0. 3 g thiourea from the resin column with recoveries of 96. 5%-99. 0%. After the chelate resin was reused for 7 times, the recoveries of these ions were still over 92%, and 400-1 000 times of excess of Fe(Ⅲ ), Al(Ⅲ ), Ni( II), Mn( Ⅱ ), Cr (Ⅲ ), Cu ( Ⅱ ), Cd (Ⅱ ) and Pb (Ⅱ ) caused little interference with the determination of these ions by an inductively coupled plasma optical emission spectrometer (ICP-OES ). The capacities of the resin for the analytes are in the range of 0. 35~0. 92 mmol/g. The RSDs of the proposed method are in the range of 1. 1 % ~4. 0% for each kind of the analyzed ions. The recoveries of a standard added in real solution samples are between 96. 5% and 98. 5%, and the results for the analyzed ions in a powder sample are in good agreement with their reported values.

硝化抑制剂双氰胺施用对水稻产量和温室气体排放的影响

为探究施用硝化抑制剂双氰胺对水稻产量和温室气体排放的影响,以常规粳稻品种南粳9108为供试材料进行盆栽试验,设置常规氮肥(CK)和常规氮肥配施硝化抑制剂双氰胺(DCD)2个处理。采用静态箱-气相色谱法连续监测稻田温室气体排放动态变化。结果表明,与CK相比,DCD显著提高了水稻产量(15.1%)和地上部生物量(28.4%),并且显著降低了稻田甲烷(CH_(4))累积排放量(22.2%)、氧化亚氮(N_(2)O)累积排放量(56.0%)、综合温室效应(GWP)(24.4%)和温室气体排放强度(GHGI)(31.7%)。可见,常规氮肥配施硝化抑制剂双氰胺可以协同实现水稻丰产和稻田温室气体减排。

硝化抑制剂双氰胺对类珠藻(固氮蓝藻)生长和生理生化特征的影响

为了阐明硝化抑制剂双氰胺(DCD)对稻田固氮蓝藻生长和生理生化特征的影响,为二者在稻田的合理使用提供理论依据,本文研究了DCD胁迫下稻田固氮蓝藻——类珠藻(Aliinostoc sp.YYLX235)的生长、光合作用、固氮酶活性、抗氧化酶活性和氧化损伤特征。结果表明,100~300 mg·L^(-1)DCD对类珠藻的生长具有明显的抑制作用。当DCD浓度为50 mg·L^(-1)时,类珠藻的细胞活力和固氮活性均显著降低。类珠藻光合系统对DCD胁迫表现出应激效应,具体表现为光合色素含量增加、光合系统Ⅱ电子传递效率提高。类珠藻细胞内超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性与培养体系DCD浓度呈正相关;当DCD浓度为200~300 mg·L^(-1)时,类珠藻细胞内氧化-抗氧化系统失去平衡,藻细胞受到氧化性损伤。DCD对类珠藻的固氮活性具有极强的抑制效应。本研究结果显示,硝化抑制剂DCD对农田固氮蓝藻的生长、细胞活力和固氮活力均具有较强的负面影响,在生产过程中固氮蓝藻菌肥需要与DCD错峰使用。

不同氮素管理模式对黄土旱塬春玉米产量及N_(2)O排放的影响

【目的】探讨不同氮素管理模式对玉米产量、N_(2)O排放的影响,为黄土旱塬区合理施用氮肥和减缓温室气体排放提供理论依据。【方法】依托中国科学院长武黄土高原农业生态试验站,以春玉米先玉335为研究对象,开展为期2年的田间定位试验。试验共设置5种不同氮素管理模式:不施氮(no fertilizer)、传统施氮(Con,250 kg N·hm^(-2))、减量施氮(Opt,200 kg N·hm^(-2))、减量施氮+缓控释肥(Opt+SR,200 kg N·hm^(-2))、减量施氮+硝化抑制剂(Opt+DCD,200 kg N·hm^(-2))。用静态箱-气相色谱法监测N_(2)O排放通量,并计算全球增温潜势和N_(2)O气体排放强度,分析不同氮素管理模式对春玉米产量和N_(2)O排放的影响。【结果】(1)氮肥施用后N_(2)O排放迅速升高,在施肥后2 d左右达到峰值,维持10 d后快速下降。减量施氮模式显著降低N_(2)O排放量(P<0.05)。与Con处理相比,Opt、Opt+DCD和Opt+SR处理N_(2)O排放量降低幅度分别为21.4%、27.6%和26.0%。Con、Opt、Opt+DCD和Opt+SR处理的N_(2)O增温潜势依次为425.01、334.01、307.83、314.57 kg CO_(2)-eq·hm^(-2)。与Con处理相比,Opt+DCD显著降低了N_(2)O排放强度,降幅为30.1%(P<0.05)。(2)N_(2)O排放量与表层土壤NH4+-N含量呈极显著正相关(P<0.01),而与土壤水分、温度无明显相关性。(3)与Con处理相比,Opt、Opt+DCD和Opt+SR处理能显著提高氮肥农学效率(增幅依次为25.5%、25.7%、22.2%)及氮肥偏生产力(增幅依次为29.9%、28.7%、25.4%)(P<0.05),但对春玉米的产量无显著影响。【结论】在黄土旱塬地区,适当减量施氮、缓控释肥及添加硝化抑制剂均能取得N_(2)O减排和玉米增产的效果,其中减氮20%并添加硝化抑制剂在保证玉米产量的同时,N_(2)O减排效果最好。

改性双氰胺固化环氧树脂研究进展

双氰胺作为最早的潜伏性固化剂之一,其固化后的环氧树脂具有优异的机械性能,但仍然有固化温度过高等缺陷。针对这一缺陷,本文从降低双氰胺上氰基的吸电子能力进而增强固化活性以及引入相似基团增强双氰胺和环氧树脂的相容性两方面对国内外文献进行归纳总结,并对改性双氰胺固化后的环氧树脂的应用进行了展望。

电接枝双氰胺改性碳纤维海洋电场电极的制备及其电场响应性能研究

碳纤维电极表面氨基改性可以显著提高其电化学性能和电场响应性能。通过控制接枝电压(3,5,7)V,在碳纤维表面接枝聚双氰胺薄膜调控电极/海水界面双电层结构和电化学性能。结果表明,接枝电位越高,碳纤维表面聚双氰胺薄膜越均匀,电极双电层结构越稳定。其中CF-7V的综合性能最佳,其比电容达到9.368 F·g^(-1),为空白组的31.6倍;电荷转移电阻和低频容抗显著降低;7天电位漂移量为1.68 mV,可以正常响应1×10^(-3)Hz,0.03 mV/m的低频弱电场信号,电极的响应灵敏度、准确度得到了显著提高。电接枝改性后碳纤维电极的电场响应性能与Ag/AgCl电极相当,这是一种新型高性能海洋电场传感器,可望提高海洋电场探测能力。

双氰胺及其尿素法工艺探讨

介绍了双氰胺及其生产工艺,特别是近年来受到关注的尿素法生产双氰胺工艺,探讨了尿素法生产双氰胺一些工艺问题,并就尾气处理工艺提出了建议。

硝酸胍精制工艺的研究

本论文介绍了当前采用传统路线双氰胺法合成的粗硝酸胍精制工艺进行探究,研究表明,无机碱的加入与活性炭的加入对粗硝酸胍精制工艺的影响较大。经过对各项工艺参数的试验,精制条件为:含量92%左右的粗产品硝酸胍在90℃~100℃的水温下溶解1 h左右,并加入0.030%~0.035%的活性炭除杂,降温后,在40.0℃左右加入0.030%的无机碱,在不断搅拌,结晶5 h后提纯脱水干燥,硝酸胍的含量可达到98.5%左右,基本达到优级品的标准。

改性双氰胺-甲醛絮凝剂的制备与性能研究

为改善双氰胺-甲醛絮凝剂(DCDF)沉降慢、对废水pH适应性差等不足,扩大其在污水处理领域中的运用,采用对氨基苯磺酸钠进行改性,合成了一种两性脱色絮凝剂SPAS-DCDF。考察了投加量、废水初始pH值等对染料脱色效果的影响,结果表明改性后的双氰胺-甲醛絮凝剂对活性红X-3B的脱色率显著上升,在酸性至弱碱性的条件下均保持良好的脱色絮凝效果。对吸附过程进行了吸附等温线和吸附动力学模型拟合,探究了吸附反应的机理,结果表明,吸附过程为单分子层主导的化学吸附,吸附速率由表面吸附点位与内扩散共同控制,理论平衡吸附量为1.2675 mg/mg,吸附过程分为三个阶段,k_(p 1)、k_(p 2)和k_(p 3)分别为0.14,0.057和0.0064 mg/(mg·min^(1/2))。

硫氰酸铵辅助双氰胺制备g-C_(3)N_(4)及其光催化性能研究

以双氰胺和硫氰酸铵为前驱体,将它们按照不同的质量比混合,600℃高温煅烧制备g-C_(3)N_(4)同型异质结复合材料光催化剂。采用X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、傅立叶红外光谱仪(FTIR)、紫外-可见漫反射吸收光谱仪(UV-vis DRS)等对制备的材料进行了表征分析。以罗丹明B为模拟污染物,考察了制备的g-C_(3)N_(4)在可见光(λ>420 nm)下的催化活性及循环利用稳定性。通过活性物种捕捉实验探寻其降解机理,结果表明,双氰胺与硫氰酸铵按3∶2混合制备的g-C_(3)N_(4)的光催化降解罗丹明B的效率2 h达到了92.53%,是纯双氰胺制备的g-C_(3)N_(4)的1.35倍,是纯硫氰酸铵制备的g-C_(3)N_(4)的1.75倍。以双氰胺和硫氰酸铵为前驱体制备的g-C_(3)N_(4)是同型异质结,提高了光生载流子的分离效率,活性物种捕捉实验表明对催化活性起主要作用的是超氧自由基(·O_(2)^(-))。

金属离子改性HZSM-5对尿素热解制氰胺反应的影响

采用不同金属离子对HZSM-5进行离子交换改性,探究不同金属离子和不同浓度锰离子交换改性对尿素转化率、单氰胺和双氰胺选择性的影响。通过XRD、NH_(3)-TPD、ICP-OES等测试对催化剂进行了表征,考察了不同离子和不同离子浓度交换对催化剂结构和酸类型、酸强度、酸中心数量的影响,并对催化剂性质与反应活性和选择性的关系进行了探究。结果表明,弱酸和中强酸为反应活性中心,B/L值高有利于尿素热解制单氰胺和双氰胺。不同浓度Mn离子改性,最佳浓度为0.2 mol/L。CeMn双金属改性ZSM-5具有良好催化效果,单双氰胺总选择性优于单一金属离子交换。

尿素硝酸铵溶液对玉米产量、养分吸收及潮土氮素积累的影响

采用大田试验,设置对照(CK,不施氮肥)、尿素处理(U,纯N 240 kg/hm^(2))、尿素硝酸铵溶液处理(UAN,纯N 240 kg/hm^(2))、80%UAN处理(80%UAN,纯N 192 kg/hm^(2))和80%UAN配施双氰胺处理(80%UAN+DCD,DCD用量为12 kg/hm^(2))共5个处理,研究不同用量UAN对玉米产量、养分吸收及潮土氮素积累的影响。结果表明:U处理和UAN各处理间玉米穗长、行粒数、千粒重和产量无显著差异,但UAN各处理株高均显著高于U处理。U及UAN各处理间玉米总吸氮量无显著差异,但U、UAN处理氮素农学效率、氮素利用率和氮素偏生产力显著低于80%UAN和80%UAN+DCD处理。各处理土壤硝态氮含量表现为U>UAN>80%UAN+DCD>80%UAN。UAN处理土壤铵态氮含量明显高于其他施氮处理,80%UAN+DCD处理土壤铵态氮含量高于80%UAN处理。各施氮处理土壤铵态氮积累量为0.10~0.73 kg/hm^(2),UAN处理积累量最高,80%UAN+DCD处理最低;各施氮处理土壤硝态氮积累量为5.70~9.19 kg/hm^(2),U处理积累量最高,80%UAN处理最低。等氮量投入条件下,氮肥形态对玉米产量及构成因素、氮素农学效率、氮素利用率和氮素偏生产力无显著影响;80%UAN及添加DCD可显著提高氮素农学效率、氮素利用率和氮素偏生产力。UAN减量及配施DCD可降低土壤中硝态氮和铵态氮的迁移积累。综合农学和环境效应来看,在本试验条件下,UAN减量20%配施DCD是一种较为科学合理的施肥管理方式。

Effect of phosphogypsum and dicyandiamide as additives on NH_3,N_2O and CH_4 emissions during composting

A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide （DCD, C2 H4 N4 ） as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N20 emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N20 emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3 , CH4 and N20 emissions.0ptimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study.

脲促进双氰胺固化多官能环氧树脂性能的研究

在萘环/缩水甘油胺环氧树脂(质量比约1∶7.85)存在的复合物中,利用双氰胺(DICY)为固化剂,不同取代脲为固化促进剂,通过差示扫描量热仪(DSC)对比了其反应活性,热机械分析仪(TMA)对比了其玻璃化转变温度和线膨胀系数,热重分析仪(TG)对比了热失重,最后测试了拉伸剪切强度。结果表明,脲单独作为固化促进剂的双氰胺体系,当同时含缩水甘油醚和缩水甘油胺的多官能环氧树脂为主体树脂时,其DSC具有双峰表明环氧基的活性差异较大,更高的后固化温度有利于提高其耐热性能和拉伸剪切强度;芳香族脲(UR200、UR300、UR500、U-52M)比脂环族脲(U-35M)具有更加优异的耐热性能;对于改善复合物的耐高温黏接性能来说,UR300是最好的,其次是U-52M。

角蛋白/双氰胺树脂复合材料的制备与性能

为了合理利用废牛毛,采用双氰胺树脂改性废牛毛水解角蛋白制备蛋白填料,并回用于制革复鞣填充工序。角蛋白/双氰胺树脂复合材料最佳制备条件为角蛋白∶双氰胺树脂为80∶20,时间4 h,pH值为7,复合材料粒径为741.5 nm,粒径分布系数为0.154,zeta电位为-19.1 mV。同时,角蛋白/双氰胺树脂复合材料具有良好的填充性能,用于黄牛鞋面革的填充工序撕裂力、抗张强度、崩破强度均有所提高。

药物中间体二苯甲基-3-氰基胍的制备

本文以二苯基甲胺盐酸盐和二氰胺钠为原料,在正丁醇溶剂中合成了药物中间体二苯甲基-3-氰基胍。采用单因素研究法,探究了反应物配比、反应温度、反应时间、溶剂用量对产品收率的影响。最佳制备工艺条件为:反应时间为6h,n(二苯甲胺盐酸盐)∶n(二氰胺钠)=1∶1.15,反应温度为120℃,溶剂用量为50m L,此条件下的收率为94%。在此基础上进行了底物拓展研究。对粗产品进行了分离精制,对纯化的产品进行了IR分析、^(1)H NMR及^(13)C NMR结构表征。结果表明,制备的产物与预期的结构相符。

Impact of dicyandiamide on emissions of nitrous oxide,nitric oxide and ammonia from agricultural field in the North China Plain

Nitrous oxide（N_2O）, nitric oxide（NO） and ammonia（NH_3） emissions from an agricultural field in the North China Plain were compared for three treatments during a whole maize growing period from 26 June to 11 October, 2012. Compared with the control treatment（without fertilization, designated as CK）, remarkable pulse emissions of N_2O, NO and NH_3 were observed from the normal fertilization treatment（designated as NP） just after fertilization, whereas only N_2O and NH_3 pulse emissions were evident from the nitrification inhibitor treatment（designated as ND）. The reduction proportions of N_2O and NO emissions from the ND treatment compared to those from the NP treatment during the whole maize growing period were 31% and 100%, respectively. A measurable increase of NH_3 emission from the ND treatment was found with a cumulative NH_3 emission of 3.8 ± 1.2 kg N/ha,which was 1.4 times greater than that from the NP treatment（2.7 ± 0.7 kg N/ha）.